Roland Brown is smitten by the Douglas flat twin… here he tells us why.

Cruising along, with the speedometer in its big nacelle reading about 50mph, the elderly Douglas felt so smooth and stable that I couldn't help being impressed. For a bike approaching its 50th birthday, the 350cc flat twin seemed like a sophisticated and efficient machine that must surely have been an excellent all-rounder back in the mid-50s.
The Dragonfly was comfortable, too, thanks to a roomy riding position and reasonably good suspension. And I'm sure I can't be the only one who finds its look curiously attractive, especially the distinctive way in which the nacelle leads into the large, rounded petrol tank.

Above: A much cleaner and tidier engine unit than, say, a non-unit type…

But if my impression of the Dragonfly was positive, that wasn't how most motorcyclists regarded the bike back in 1955. Instead of being a big a success, the Dragonfly sold so slowly following its introduction that Douglas – which had built its first bike back in 1907 and had won the Junior TT as long ago as 1912 – was taken over in 1956, and ceased bike production altogether a year later.
Such a hasty demise doesn't reflect well on the Dragonfly, and perhaps the bike's weakness was exposed when, shortly after my ride, I sat down to make some notes – and had trouble remembering very much about the experience. Smoothness and efficiency are all very well in a motorcycle, but plenty of rival bikes provided a lot more performance and excitement than the Dragonfly.
It would be wrong to blame the Dragonfly for causing the end of Douglas, though, because the Bristol firm had been struggling for years. Its high point had arguably come in 1923, with victories in both the Senior and Sidecar TTs, the latter with an innovative leaning outfit piloted by Freddie Dixon. But Douglas had later suffered a string of financial collapses, notably in 1937 following the deaths of founder members William Douglas and his son John.
Despite that setback Douglas had a reasonably successful WWII, gaining work with trucks, aircraft parts and generators. The firm had always been versatile, having built cars and tractors, among other things, in its early days. After WWII Douglas recommenced bike production with a new model called the T35, whose 348cc flat twin motor was based on the generator – not the most promising heritage! The twin-downtube frame was developed from that of the Endeavour, which had been Douglas's first flat twin with BMW-style transverse cylinders when launched in 1934.
The T35 stood out when launched in 1947, because most rival British bikes were simple rigid-framed singles. By comparison, designer George Halliday's machine seemed relatively sophisticated, despite its engine's humble origins. As well as its twin-cylinder powerplant, it featured a patented torsion bar (twisting metal rods) suspension system at both ends. But the T35 suffered with a number of problems. Various minor design flaws, poor quality control and use of sub-standard materials combined to give Douglas a reputation for unreliability.
The T35 was improved over the years, being produced in a series of updated versions, beginning with the MkII and ending with the MkV. But Douglas was in a worse financial position than ever by the time the MkIII model was launched in 1948, and the firm went into receivership later that year. Although production continued, expenditure was severely restricted and there was little chance of a full recovery.
Some racing and development work continued, under the control of former race ace Freddie Dixon. In 1950 the firm introduced two sporty versions of the T35, the 80 Plus and 90 Plus, named after their claimed top speeds of 80mph and 90mph. Engine changes for both included new cylinder heads, extra cooling fins and a strengthened crankshaft. In addition the 90 Plus had higher compression ratio, and each motor was dyno tested to confirm it produced at least 25bhp. The 90 Plus just about lived up to its name, which meant it performed pretty well, but Douglas continued to struggle in the early 1950s.
Hopes were boosted in 1954 with the unveiling of the Dragonfly, which combined a new chassis with a modified version of the 348cc engine. When launched at that year's Earls Court Show, the model made quite an impact, largely due to its striking styling. The sheet-steel nacelle held the 80mph speedo, a smaller ammeter and the ignition switch, as well as the headlamp.
The new engine retained the traditional T35 capacity of 348cc from near-square dimensions of 60 x 60.8mm, but was influenced both by the 90 Plus and a 500cc prototype that had been developed and then abandoned a few years earlier. Its cylinder heads were based on those of the 500, while the bottom end was strengthened in 90 Plus style with stronger crankcase webs and uprated lubrication system.
Like the T35, the Dragonfly used chain final drive rather than a BMW-style shaft. Because the crankshaft was in line with the bike, this required a bevel-gear system between the four-speed gearbox and the front sprocket, to turn the drive through 90-degrees. The rectifier and coil were located under the large petrol tank; other electrical components lived on top of the engine, under an alloy plate that helped give the powerplant a notably smooth look.
The twin-downtube frame and the front suspension were built by chassis specialist Reynolds. The front suspension system, as fitted to BMWs, was the pivoted, twin-shock system designed by Ernie Earles, who had also styled the Dragonfly's nacelle. At the rear, twin shocks replaced Douglas's previous torsion bar suspension system, and were a sophisticated feature at the time. At 365lb dry weight the Dragonfly was slightly heavier than the T35 MkV, but was respectably light given its sturdy chassis.

END OF ONLINE SAMPLE | BACK TO FEATURE INDEX